a couple of things
there was mention of 60,000 (6013) vs 70,000 (7018) and that a good 6013 is better than a not so good 7018.
well, maybe and maybe not.
the first two digits are the tensile strength.
this is not such a big factor when the steel you are welding has a tensile strength of not more than 42,000.
they are both over kill when it comes to tensile strength.
something more important to look at is the impact strength and dynamic vs static loading.
7018 has much better properties in cold conditions than S-3 or S-6 solid wire or 6010, 6011, or 6013 stick.
it performs better on the critical moving parts such as the ram, guides and wedges.
also, my two cents on a couple of other comments.
unless you have an open root joint, there is no need to use a 6010 root and cover with 7018.
weld it all up with 7018 and be done with it.
if you can, use gas shielded FCAW ... not self shielded FCAW.
it costs more, but you get much better welds.
Garn uses Hobart Fabco 71 to weld their boilers.
it costs them more to do so, but the welds are far superior to their competitors solid wire welded boilers.
no cold lap welds in their boilers.